There are instances when it is desired to connect an electrical load to a live electrical power source or power supply (either AC or DC) that is already on. This can give rise to large in-rush currents as capacitive components of the load charge up. Such capacitive components may be real or parasitic components.
These in-rush currents can perturb the operation of the source and the load, possibly causing protective measures within the circuit to trip. Furthermore, the in-rush currents may introduce perturbations in the power supplied to other loads connected to the power supply, and these perturbations may affect the operation of those circuits. In addition, if the newly introduced load is faulty, its fault may also affect the operation of the power supply and the other loads or circuits connected to the supply. In order to address these issues, “hot swap” circuits can regulate or control the current flow to a load that is newly introduced to a power supply that allows the load to the powered up safely.